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23 Cards in this Set
- Front
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What is true of microevolution?
It is evolution that involves only tiny changes to DNA, such as point mutations, producing only small (if any) changes to phenotype. It is evolution that results in the origin of small numbers of new species. It is evolution that influences only a small subset of the populations that comprise a species. It is the kind of evolution that can change the relative abundance of a particular allele in a gene pool over the course of generations. It is evolution that is restricted to individual organisms. |
It is the kind of evolution that can change the relative abundance of a particular allele in a gene pool over the course of generations.
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The original source of all genetic variation is _____.
recombination independent assortment mutation natural selection sexual reproduction |
mutation |
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How does diploidy help to preserve genetic variation?
It allows recessive alleles that may not be favored in the current environment to be preserved in the gene pool by propagation in heterozygotes. It restricts the gene pool by chance events such as floods or other catastrophic events. It fosters the exchange of genes between different populations. It allows the frequency of a recessive allele in a population to be predicted under certain conditions. It helps individual organisms make a greater contribution to the gene pool of the next generation. |
It allows recessive alleles that may not be favored in the current environment to be preserved in the gene pool by propagation in heterozygotes
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Blue poppies native to China were grown at a plant-breeding center in California. The plants with the thickest leaves were most likely to survive and reproduce in the drier climate. After several generations, the percentage of thick-leaved plants had increased by 42%. This adaptation of the poppies to their new environment is due to _____.
stabilizing selection genetic drift neutral variation directional selection disruptive selection |
directional selection |
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Natural selection changes allele frequencies because some _______ survive and reproduce more successfully than others.
individuals species gene pools alleles loci |
individuals |
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According to the Hardy-Weinberg theorem, the frequencies of alleles in a population will remain constant if _____ is the only process that affects the gene pool.
immigration sexual reproduction sexual selection genetic drift mutation |
sexual reproduction |
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No two people are genetically identical, except for identical twins. The main source of genetic variation among human individuals is
environmental effects. geographic variation within the population. genetic drift due to the small size of the population. new mutations that occurred in the preceding generation. the reshuffling of alleles in sexual reproduction. |
the reshuffling of alleles in sexual reproduction |
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If the nucleotide variability of a locus equals 0%, what is the gene variability and number of alleles at that locus?
Without more information, gene variability and number of alleles cannot be determined. gene variability > 0%; number of alleles = 2 gene variability = 0%; number of alleles = 0 gene variability = 0%; number of alleles = 1 gene variability = 0%; number of alleles = 2 |
gene variability = 0%; number of alleles = 1
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There are 40 individuals in population 1, all with genotype A1A1, and there are 25 individuals in population 2, all with genotype A2A2. Assume that these populations are located far from each other and that their environmental conditions are very similar. Based on the information given here, the observed genetic variation is most likely an example of
discrete variation. disruptive selection. directional selection. genetic drift. gene flow. |
genetic drift
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The fruit fly Drosophila melanogaster has an allele that confers resistance to DDT and similar insecticides. Laboratory strains of D. melanogaster have been established from flies collected in the wild in the 1930s (before the widespread use of insecticides) and the 1960s (after 20 years of DDT use). Lab strains established in the 1930s have no alleles for DDT resistance. In lab strains established in the 1960s, the frequency of the DDT-resistance allele is 37%. Which statement is correct?
Alleles for DDT resistance arose by mutation during the period of DDT use because of selection for pesticide resistance. The evolutionary fitness associated with the heritable trait of DDT resistance changed once DDT use became widespread. Resistance to DDT evolved in some fruit flies in order to allow them to survive. |
The evolutionary fitness associated with the heritable trait of DDT resistance changed once DDT use became widespread
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One out of 10,000 babies born in North America is affected by cystic fibrosis, a recessive condition. Assuming that the North American human population is in Hardy-Weinberg equilibrium for this trait, what percentage of the population is heterozygous for this trait? (Remember the equation for a population in Hardy-Weinberg equilibrium: p2 + 2pq + q2 = 1.)
0.01% 2% 1% |
2%
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Which statement correctly describes the role of chance in evolution?
The ultimate source of new alleles is mutation, random changes in the nucleotide sequences of an organism’s DNA. An allele that increases evolutionary fitness cannot be lost from a population by chance events. Evolution by natural selection proceeds by an accumulation of changes that occur by chance. |
The ultimate source of new alleles is mutation, random changes in the nucleotide sequences of an organism’s DNA
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What is the most important factor that holds a gene pool of a species together and prevents speciation?
sexual selection prezygotic barriers hybridization behavioral isolation gene flow |
gene flow
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Two animals are considered members of different species if they _____.
live in different habitats look different cannot mate and produce viable, fertile offspring are geographically isolated are members of different populations |
cannot mate and produce viable, fertile offspring
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Hybrid zones provide an opportunity to investigate _____.
the evolution of reproductive isolation punctuated equilibrium polyploidy mutations allopatric speciation |
the evolution of reproductive isolation
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A certain species of salamander was split into two populations by a wide, dry valley, and the populations began to diverge from each other. After a period of time, some members of the two populations began to interbreed in a hybrid zone at the southern end of the valley. Only weak reproductive barriers existed by this time, so the two populations could freely interbreed and re-establish gene flow. This outcome in a hybrid zone is known as _____.
punctuated equilibrium reinforcement speciation stability fusion |
fusion
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According to the _____ model, evolution occurs in spurts; species evolve relatively rapidly then remain unchanged for long periods.
gradualist nondisjunction punctuated equilibrium geographic isolation adaptive radiation |
punctuated equilibrium
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Adaptive radiations on archipelagos (island chains) represent some of the best-understood speciation events. Why is an ancestral species more likely to give rise to multiple descendent species on an archipelago than on an equal-sized area of mainland?
By chance, different species will colonize different islands in a chain. Populations on nearby islands are more likely to be genetically isolated than populations that are equally close to one another on the mainland. Favorable mutations are more likely to arise on an archipelago as populations try to adapt to conditions on their specific island. |
Populations on nearby islands are more likely to be genetically isolated than populations that are equally close to one another on the mainland.
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Select the correct statement describing sympatric speciation.
Sympatric speciation has never been observed in nature. Sympatric speciation can occur in a single generation. Sympatric speciation is always initiated by geographic isolation of two populations. |
Sympatric speciation can occur in a single generation
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Males of different species of the fruit fly Drosophila that live in the same parts of the Hawaiian Islands have different elaborate courtship rituals. These rituals involve fighting other males and making stylized movements that attract females. What type of reproductive isolation does this represent?
postzygotic barriers behavioral isolation gametic isolation temporal isolation habitat isolation |
behavioral isolation
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According to the punctuated equilibria model,
natural selection is unimportant as a mechanism of evolution. most evolution occurs in sympatric populations. given enough time, most existing species will branch gradually into new species. speciation is usually due to a single mutation. most new species accumulate their unique features relatively rapidly as they come into existence, then change little for the rest of their duration as a species |
most new species accumulate their unique features relatively rapidly as they come into existence, then change little for the rest of their duration as a species.
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Bird guides once listed the myrtle warbler and Audubon's warbler as distinct species. Recently, these birds have been classified as eastern and western forms of a single species, the yellow-rumped warbler. Which of the following pieces of evidence, if true, would be cause for this reclassification?
The two forms live in similar habitats. The two forms are very similar in coloration. The two forms have similar food requirements. The two forms have many genes in common. The two forms interbreed often in nature, and their offspring have good survival and reproduction. |
The two forms interbreed often in nature, and their offspring have good survival and reproduction
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Which of the following factors would not contribute to allopatric speciation?
The separated population is small, and genetic drift occurs. A population becomes geographically isolated from the parent population. Different mutations begin to distinguish the gene pools of the separated populations. Gene flow between the two populations is extensive. The isolated population is exposed to different selection pressures than the ancestral population |
Gene flow between the two populations is extensive.
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